Natural selection occurs when one allele (or combination of alleles of different genes) makes an organism more or less fit, that it is able to survive and reproduce in a given environment. If an allele reduces fitness, its frequency will tend to drop from one generation to the next.
The bee at the right is looking for nectar in a flower. While looking for food, this bee is also pollinating the flowers by transferring pollen from the ___anthers__ on one flower to the __stigma__ on another flower.
